CVE-2026-63831: mac802154: llsec: add skb_cow_data() before in-place crypto

CVE-2026-63831: mac802154: llsec: add skb_cow_data() before in-place crypto

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

mac802154: llsec: add skb_cow_data() before in-place crypto

llsec_do_encrypt_unauth(), llsec_do_encrypt_auth(),
llsec_do_decrypt_unauth(), and llsec_do_decrypt_auth() all perform
in-place cryptographic transformations on skb data.  They build a
scatterlist with sg_init_one() pointing into the skb's linear data area
and then pass the same scatterlist as both src and dst to the crypto API
(e.g. crypto_skcipher_encrypt/decrypt, crypto_aead_encrypt/decrypt).

On the RX path, __ieee802154_rx_handle_packet() clones the received skb
before handing it to each subscriber via ieee802154_subif_frame().  The
cloned skb shares the same underlying data buffer via reference
counting.  When llsec_do_decrypt() subsequently modifies this shared
buffer in place, it corrupts data that other clones -- potentially
belonging to other sockets or subsystems -- still reference.

On the TX path, similar data sharing can occur when an skb's head has
been cloned (skb_cloned() returns true).

The fix is to call skb_cow_data() before performing any in-place crypto
operation.  skb_cow_data() ensures that the skb's data area is not
shared: if the skb head is cloned or the data spans multiple fragments,
it copies the data into a private buffer that can be safely modified in
place.  This is the same pattern used by:

  - ESP (net/ipv4/esp4.c, net/ipv6/esp6.c)
  - MACsec (drivers/net/macsec.c)
  - WireGuard (drivers/net/wireguard/receive.c)
  - TIPC (net/tipc/crypto.c)

Without this guard, in-place crypto on shared skb data leads to:
  - Silent data corruption of other skb clones
  - Use-after-free when the crypto API scatterwalk writes through a
    page that has already been freed by another clone's kfree_skb()
  - Kernel crashes under concurrent 802.15.4 traffic with security
    enabled (KASAN/KMSAN reports slab-use-after-free)

Found by 0sec (https://0sec.ai) using automated source analysis.

The Linux kernel CVE team has assigned CVE-2026-63831 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 5.10.260 with commit 3a2b378b3a9ca75d3518d879148d2ad25b5714a9
	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 5.15.211 with commit 7a831bcd0486788283ef35e396d4282ee01bb0d5
	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 6.1.177 with commit ff976ef7c39199ebff33c18034636595016db9f0
	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 6.6.144 with commit e28e7fd34c449028325322a3f5127b92594b7396
	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 6.12.95 with commit 993fd674fe85d114e6a8d3963033d4fbbc2170a8
	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 6.18.38 with commit bd968bdd568beacfdf98ec537a87527e85f1d0cf
	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 7.1.3 with commit 86d531337ea1ba02d9f2bc830d07c683d9bfaade
	Issue introduced in 3.16 with commit 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 and fixed in 7.2-rc1 with commit 84a04eb5b210643bd67aab81ff805d32f62aa865

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-63831
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/mac802154/llsec.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/3a2b378b3a9ca75d3518d879148d2ad25b5714a9
	https://git.kernel.org/stable/c/7a831bcd0486788283ef35e396d4282ee01bb0d5
	https://git.kernel.org/stable/c/ff976ef7c39199ebff33c18034636595016db9f0
	https://git.kernel.org/stable/c/e28e7fd34c449028325322a3f5127b92594b7396
	https://git.kernel.org/stable/c/993fd674fe85d114e6a8d3963033d4fbbc2170a8
	https://git.kernel.org/stable/c/bd968bdd568beacfdf98ec537a87527e85f1d0cf
	https://git.kernel.org/stable/c/86d531337ea1ba02d9f2bc830d07c683d9bfaade
	https://git.kernel.org/stable/c/84a04eb5b210643bd67aab81ff805d32f62aa865